Why does it seem so much easier for some people to know which course to follow, even if it involves the complex emotions and uncertain outcome of war?
Why are some people able to look at the evidence in support of the war in Iraq and conclude the war is totally justified, while others look at essentially the same evidence and reach the opposite conclusion?
Why do reasonable people disagree?
And why are some people so ambivalent, acting as though they are "of two minds," as the old saying goes?
Maybe because they are. New research by scientists at several institutions indicates that the human brain does not act as a single processing unit, but instead has at least two neural networks that may be either helping or competing with each other as we try to figure out who's right in this deadly struggle.
Separate Networks Making Decisions
Psychologist Kip Smith of Kansas State University did not address indecision about the war in his study, but the preliminary findings of his team indicate that the human cognitive process is far more complex than had been thought. The researchers have identified two separate neural networks, one deliberative and relatively young in our evolutionary development, the other emotional and quite old.
"There is not a single executive decision-making mechanism" in the human brain, Smith says. "We're of at least two minds."
And those minds may not always agree.
This is the first step in a long high-tech process to learn how we make decisions on issues ranging from simple to complex.
"We've just started," Smith says. "This is the first salvo in a whole campaign to find out how this [the decision-making process] works."
The researchers used positron emission tomography to produce images that show where blood is going in the brain. The assumption, Smith says, is blood-flow correlates with high neural activity, so areas receiving an increase in blood are reacting to a stimulus, in this case questions involving risk, gain, loss and ambiguity.
The Simple Stuff
The images from the experiment revealed two distinct regions in the brain, or networks, that responded to questions involving such things as whether the participant was willing to take a small gamble in hopes of winning a few bucks.
"We found two different patterns of activation for dealing with this stuff," Smith says.
One network is an older structure in the brain that "lit up" when the participants were presented with risky gains.
"That part of the brain is present in lesser mammals," Smith says, and it tells us and other critters to go for the sure thing rather than take a chance.
"A bird in the hand is worth two in the bush," he says. "It makes great sense that evolution would have built such a machine, or system, to deal with risky situations. I will eat this banana now instead of trying to get to that papaya that's way up the tree. I don't have to think hard about that.
The Heavy Lifting
"The younger part of the brain deals with losses and ambiguity and these much more complicated issues," he adds. That's the part of the brain that handles mathematics and abstract reasoning, and it's what sets us apart from other animals.
"What we have shown is there is a part of the brain that is involved in making simple economic decisions that is closely tied in to the parts of the brain that process emotions," Smith says. "We've also shown that for the same economic decisions, there's a part of the brain that is known to be involved in mathematics and other higher reasoning processes.
"The behavior they generate is often the same," at least for the level of mental activity required for the experiment.
In the neuroimaging experiment, both "minds" seemed to work together without any serious conflict. But Smith speculates that in the real world, that may not always be the case.
Participants in the study were presented with relatively simple and straightforward issues, and that may have "predisposed" them to use the more rational part of their brains, he says.
"Many situations in real life are not as formally simple as the stimuli we gave our subjects," he says. Taking a giant leap beyond the limits of his current research, Smith says it's possible that in a more complex setting the two networks might get into a bit of a fight themselves.
Our more primitive mind might overwhelm our more modern mind, making us more reactive than rational. Or our mathematical mind might tell us to take the gamble and ignore the risk. Yet at least some of the time we're probably getting conflicting signals from both "minds."
"This could say why some people are conflicted about this war," he says. "We all, in our gut, want our men and women to do well, but in our lofty heads, this ivory tower, we're saying why in the hell are we there in the first place."
Many are, as the man says, of at least two minds.
Results of the study were published in the journal Management Science. In addition to Smith, the team included John Dickhaut of the University of Minnesota, Kevin McCabe of George Mason University, and Jose V. Pardo of the Veterans Affairs Medical Center and the University of Minnesota.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.